The art of the present invention relates to torsional dissection tips in general and more particularly to a tip for a linear or longitudinal ultrasonic generator which provides uniquely patterned and formed teeth which are able to uniquely provide torsional and linear dissection of hard or dense biological tissues including intracranial bone. The present art embodiments utilize a unique substantially pineapple shaped head. The art of the present invention is especially suited for dissection of bone and calcified neoplasm during neurosurgery, spinal surgery, orthopedic surgery, plastic/reconstructive surgery, and ear, nose, and throat surgery without the deleterious effects to nearby tissues presented with high speed drilling.
The prior art describes a longitudinal-torsional ultrasonic tissue dissection apparatus in U.S. application No. 09/833,109 filed Apr. 11, 2001 by Wuchinich, entitled Longitudinal-Torsional Ultrasonic Tissue Dissection published Nov. 29, 2001 with U.S. publication number 2001/0047166 A1. The aforesaid prior art describes an apparatus for providing torsional movement from a longitudinal ultrasonic generator but fails to provide optimum cutting teeth or head design for hard or dense biological tissues. The prior art utilizes a series of pyramidal shaped teeth spaced apart many times the torsional and/or linear cutting displacement. The aforesaid art is only marginally effective for the intended application. The present art provides a plurality of optimally spaced teeth with a pitch corresponding to a torsional and/or longitudinal stroke of the torsional ultrasonic generator. The present art embodiments provide the aforesaid with an expanded head with pyramidal projections located circumferentially around the distal shaft orifice.
During many surgical procedures, it is necessary to remove all or a portion of a bony structure in order to provide access to other tissue or organs. In other instances it becomes necessary to shape bone to facilitate approximation of implants, autologous materials, wound closure, etc. Often the shaping or removal of the bony material is done in close proximity to fragile and/or eloquent tissues. In these instances it is desirable that the instrument used for bone removal act in a manner that is predictable and precise. Specific requirements would include, but not be limited to minimization of torque at start up to prevent displacement of the instrument from intended tissue contact, minimized, precise, and discrete tissue impact to restrict alternate site injury potentially caused by the transmitted effect of the instrument, and an overall action that allows the surgeon to focus upon the area of interest rather than having to be concerned with complications secondary to the use of the instrument.
Much of the current state of the art as it relates to these applications is found in the employment of high-speed air motors or drills. Reaching rotational speeds of up to 95,000 rpm, burrs attached to the air motor affect removal of tissue at varied rates, dependent upon the surface of the burr. Hardened steel cutting tools remove bone rapidly and diamond coated tools affect removal at a much slower rate, but do so with a greater deal of forgiveness, as there is some degree of discrimination in the diamond means of tissue destruction. The spinning burr is directed against the bone to be removed and the cutting surface cuts or grinds it away. A disadvantage of the high-speed burr is a tendency to “skip” from the bone upon initial contact or displacement of the handpiece in the direction of rotation as it contacts the surface to be removed. Due to the constant rotation of the burr, surrounding tissue and/or materials, e.g. sutures, surgical patties, etc., can be inadvertently captured by the rotating shaft of the instrument, thus pulling the tissue and/or materials around the shaft in a “spooling” action. In the case of diamond coated burrs, clearance of chips from the operative site is minimized, thereby trapping the associated heat generated by contact between the tool and the bone. As such, excessive heat generation is a genuine concern, with temperatures in excess of 180 degrees Fahrenheit having been clinically documented. As the generally accepted heat threshold for the inducement of neuronal injury is approximately 109 degrees Fahrenheit, the heat generated by a diamond tool on a high-speed air motor constitutes a genuine clinical concern.
As aforesaid, recently a means of accomplishing the aforesaid objectives has become commercially available as described in the Wuchinich application. This instrument consists of an ultrasonic motor or generator connected to a shaped tip. The motor is designed to vibrate longitudinally (along its axis), at a fixed frequency with variable amplitude. The tip is designed to convert the longitudinal vibration to a combination of longitudinal and torsional vibration. The aforesaid art teaches how to make an instrument that incorporates longitudinal-torsional motion and how this tip might then be applied to tissue. It does not describe potential tip geometry or configuration that may or may not be advantageous.
Commercially available embodiments of the aforesaid art utilize a working surface having a plurality of teeth or grooves spaced substantially greater than the torsional and/or linear cutting displacement rather than distinct substantially pyramid shaped teeth which are spaced two times or less than the aforesaid displacement. The present art utilizes a plurality of pyramid or tetrahedral shaped teeth arrayed on the working surface which are spaced in all embodiments at least two times or less than the maximum aforesaid displacement.
Accordingly, it is an object of the present invention to provide a torsional dissection tip having a plurality of optimally spaced teeth with a pitch corresponding to a torsional and/or longitudinal stroke of the torsional ultrasonic generator.
Another object of the present invention is to provide a torsional dissection tip having a plurality of optimally spaced teeth, at least two times or less than the longitudinal or torsional tool surface displacement, which may take many different forms, including but not limited to pyramid or tetrahedral shapes, yet function optimally.